The present invention relates to managing sleep and wakeup events of computers in motor vehicle CAN (“Control Area Network”) networks.
As known in itself, in a motor vehicle, many functionalities are controlled electronically with the aid of computers (injection, braking, air-conditioning, windshield wipers, etc.).
For reasons of safety or for reasons of simplicity in design, a motor vehicle is normally equipped with several CAN networks interconnected via gateways.
Furthermore, some computer controlled vehicle functionalities are intermittent, as for example the so-called “comfort” functionalities such as air-conditioning, windscreen wipers, power windows, etc. In order to save energy, when a vehicle functionality is not used, the associated computer sleeps, then wakes up when needed.
The wakeup and sleep commands for the vehicle computers are normally handled centrally by a dedicated computer, called a “master” computer and the CAN network to which it is connected is then designated the “main” CAN network. The other CAN networks of the vehicle are designated as “secondary” networks and the computers under the command of the master computer are termed “slave” computers.
For wakeup and sleep events of a slave computer, the master computer emits a command frame to its address on the main CAN network. Where necessary, the command frame passes through a gateway when the slave computer is connected to a secondary CAN network. Once received by the slave computer, the latter then emits a frame in return to the master computer confirming successful reception of the command frame, a frame that passes through the gateway where necessary.
Given the large number of computers on board the vehicle, the number of frames being carried on the main CAN network is very large. Thus risks of collision are great. The risk of a frame not being immediately taken into account by the master computer is also high when there are a large number of frames. A powerful master computer must therefore be provided in order to minimize such risks.